LOCAL COORDINATE SYSTEM

 

DSI refers to the local coordinate system to translate, rotate, mirror, copy, and generate points, lines, and nodes.   When such a function is selected, the program will automatically prompt the user to generate a local system designated as the UVW coordinate frame. One, two, or three reference points are required to establish a local coordinate system.

 

For a three-point system, the first reference point defines the local origin. The second reference, which extends from the first reference point, defines the direction of the local U-axis.  The third reference point defines the local UV plane.  The local W-axis is defined in the UV plane and is perpendicular to the U-axis.  The local W-axis is then defined according to the right hand rule perpendicular to the UV plane.

 

For the two-point option, DONE should be selected after the second reference point is defined.  The local W-axis lies along the vector from the origin to the second reference point, the V-axis lies in the VW plane, and the U-axis is defined by the right hand rule.

 

Note:   All rotational commands (generating arcs, copying with rotation, etc.) are executed about the local W- or global Z-axis.

 

For the one reference point option, the user selects a point or node on the screen as the local origin then enters one of the X, Y, or Z options that are listed to define the local W along one of the global axes.

 

1. When creating a local coordinate system, DSI prompts:

>     CREATE LOCAL COORDINATES

       PICK NODE/PT FOR ORIGIN

      DSI prompts for a desired coordinate system (local or global) in the        options area.

?     ABORT

       GLOBAL SYSTEM

       KEY IN X, Y, Z

      This signals the user to key in the origin of the local coordinate system.

>     ENTER X, Y, Z COORDINATES

•      The user enters the values for the X, Y, and Z coordinates, e.g.10,0, and 0.

NODE

•      Default

POINT

SHOW LAST C.S.

•      Once the last coordinate system has been displayed, see step 3.

•      The user may select a node or a point, enter a coordinate by keyboard, or use any combination of these options to create a local coordinate system.

2. Once a reference point has been selected, DSI prompts:

>     PICK NEXT POINT OR NODE

?     ABORT

       DONE

•     After the user selects 2 reference points, DSI displays the coordinate system and continues to step 3.

KEY IN XYZ

•      The user may enter up to 3 reference points globally to define a local coordinate system.

INCREMENTAL XYZ

•      The user may enter DX, DY, and DZ from the previous reference       point to define a local coordinate system.

NODE

•      The user may select up to 3 nodes to define a coordinate system.

POINT

•      The user may select up to 3 points to define a coordinate system.

REJECT LAST

•      This allows the user to deselect the last reference point during the   selection process.

X AS LOCAL W AXIS

•      This defines a local coordinate system that is parallel to the global axis with the local W along the global X-axis and the local origin at the first reference point.

Y AS LOCAL W AXIS

•      This defines a local coordinate system that is parallel to the global axis with the local W along the global Y-axis and the local origin at the first reference point.

Z AS LOCAL W AXIS

•      This defines a local coordinate system parallel to the global axis with the local W along the global Z-axis and the local origin at the first reference point.

 

3. Once the user defines the desired coordinate system, DSI displays it and prompts:

>     ACCEPT? (Y/N/A)

?     YES

•      DSI prompts for the next command.

NO

•      The user returns to step 1.

ABORT

•      The user returns to the menu.